determine the fate of amanda knox. the american college student who was convicted and then acquitted of murdering her roommate. the prosecutors who held her behind bars there for four years are arguing she should be returned to jail. here's abc's nick schifrin tonight. >> my family is really the most important thing right now. and i just want to go and be with them. >> reporter: amanda knox waited four years for that homecoming. but tonight, she's anxious that italy's supreme court could put her freedom in jeopardy. >> the fact that she spent three or four years in an italian prison and this murder charge continues to hang over her head. there is no peace of mind. >> i couldn't understand why they were so sure i was the one who knew everything. >> reporter: in 2007, knox and her italian boyfriend, raffaele sollecito, were convicted of murdering their roommate, meredith kercher. they languished in prison for years. the world watched the dramatic moment they were released. >> both defendants have been acquitted. >> reporter: but now, prosecutors want to reinstate the murder conviction.